1. Field of the Invention
The present invention relates to a coupling to be interposed between a driving shaft and a driven shaft, for example, a steering main shaft and a steering gear shaft in the steering system of an automobile. In particular, it relates to a coupling for transmitting torque from a driving shaft to a driven shaft through impact absorbing members of elastic material such as rubber in the small torque range and by direct contact of a member connected with the driving shaft and a member connected with the driven shaft in the large torque range and thereby absorbing or damping impacts such as vibration, a shock and a noise transmitted from the driven shaft.
2. Description of the Prior Art
Various kinds of such a coupling, i.e., a coupling having variable torsional rigidity, have heretofore been provided and put into practice for the steering system of an automobile. In the steering system of an automobile, as is well known, impacts such as vibration and a shock caused by movement of the wheels or the steering gear are transmitted through the steering main shaft to the driver holding the steering wheel and give an uncomfortable feeling to the driver. However, when the aforementioned coupling having torsional rigidity is interposed between the steering main shaft and the steering gear shaft, the impacts are effectively absorbed or damped by the coupling to give a comfortable ride feeling to the driver. In the steering system, further, a high level of rigidity is required to make the steering wheel be sharply turned. Thus, it is conditioned in the steering system of an automobile that impacts transmitted from the wheel or steering gear are effectively absorbed or damped and that the steering wheel can sharply be turned.
The various couplings heretofore provided to fulfil the aforementioned requirements are all complicated in construction and costly to produce.